The conditions upon which the survival of sign language among the Indians has depended is well shown by those attending its discontinuance among certain tribes.

Many instances are known of the discontinuance of gesture speech with no development in the native language of the gesturers, but from the invention for intercommunication of one used in common.  The Kalapuyas of Southern Oregon until recently used a sign language, but have gradually adopted for foreign intercourse the composite tongue, commonly called the Tsinuk or Chinook jargon, which probably arose for trade purposes on the Columbia River before the advent of Europeans, founded on the Tsinuk, Tsihali, Nutka, &c., but now enriched by English and French terms, and have nearly forgotten their old signs.  The prevalence of this mongrel speech, originating in the same causes that produced the pigeon-English or lingua-franca of the Orient, explains the marked scantiness of sign language among the tribes of the Northwest coast.

Where the Chinook jargon has not extended on the coast to the North, the Russian language commences, used in the same manner, but it has not reached so deeply into the interior of the continent as the Chinook, which has been largely adopted within the region bounded by the eastern line of Oregon and Washington, and has become known even to the Pai-Utes of Nevada.  The latter, however, while using it with the Oregonian tribes to their west and north, still keep up sign language for communication with the Banaks, who have not become so familiar with the Chinook.  The Alaskan tribes on the coast also used signs not more than a generation ago, as is proved by the fact that some of the older men can yet converse by this means with the natives of the interior, whom they occasionally meet.  Before the advent of the Russians the coast tribes traded their dried fish and oil for the skins and paints of the eastern tribes by visiting the latter, whom they did not allow to come to the coast, and this trade was conducted mainly in sign language.  The Russians brought a better market, so the travel to the interior ceased, and with it the necessity for the signs, which therefore gradually died out, and are little known to the present generation on the coast, though still continuing in the interior, where the inhabitants are divided by dialects.

No explanation is needed for the disuse of a language of signs for the special purpose now in question when the speech of surrounding civilization is recognized as necessary or important to be acquired, and gradually becomes known as the best common medium, even before it is actually spoken by many individuals of the several tribes.  When it has become general, signs, as systematically employed before, gradually fade away.

THEORIES ENTERTAINED RESPECTING INDIAN SIGNS.